Abrasive wheel



Oct. 6, 1931.

3 Sheets-Sheet 1 R. CHAPELL ABRASIVE WHEEL Filed Aug. 10. 1929 ."HM/MWITNESS Oct. 6, 1931. R CHAPELL 1,826,300

ABRAS IVE WHEEL Filed Aug. 10. 1929 5 Sheets-Sheet 2 fizz/' 6 I WW. 7' vINVENTO Patented .Oct. 6, 19 31 UNITED STATES PATENT OFFICE REVERECHAPELL, 0F CINCINNATI, OHIO ABRASIVE WHEEL Application filed August 10,1929. Serial No. 384,988.

operated is very high.

Heretofore, so far as I am aware, grinding wheels have been madesubstantially homo-- geneous throughout. For high speed abrasive wheelssuflicient binding material is uniformly incorporated throughout the mixto enable the finished wheel to withstand, when new, the centrifugalforce developed therein at the maximum high speed for which the wheel isdesigned to be used'; and the force of the blow or impact of theparticles of abrasive material against the metal being ground, and tofirmly hold said particles of abrasive to the wheel during their impactagainst the metal being abraded.

But in the practical use of abrasive wheels, the angular speed at whichthe wheel is rptated is determined by the surface speed at which thewheel is designed to be run when new, and the angular speed having beenthus once determined, the wheel is thereafter rotated at that fixedangular speed until it is worn out, that is to say, until the diameterhas been reduced to a point where it is unsafe to use the remaining ringof abrasive material surrounding the spindle, or to a point or zonewhereat the wheel no longer grindsefiiciently.

The point at which a. worn abrasive wheel 4 no longer cutswithefliciency, and consequently heats, increasing the liability of therupture of the wheel, is that diameter where there is an excess ofbinding material for the surface speed at which the wheel is then beingactually used. No binder commonly used is an abrasive. On the contrary,it is a friction producing material as it slides over the surface beingabraded. The friction of this excessive binding material, rubbing overthe metal being abraded, generates a large amount of heat which weakensthe wheel and increases the liability of rupture.

It is an object of my invention to obviate the difliculties aboverecited, by properly progressively increasing the strength of the bondor binding material in an abrasive wheel from the axis outwardlyradially so that there is always at the active surface of the wheel,irrespective of the diameter to which it may have been worn, asuflicient amount of and strength in the bonding material to make thewheel of that diameter safe to use at the angular speed at which thewheel is being driven, but in which there shall be no substantial excessof said bonding material at any diameter to which the wheel may be worn.

A further object of my invention is to provide the peripheral portion ofa grinding wheel, designed to be driven at a definite high surfacespeed, with a suflicient quantity of binding material for a wheel ofthat diameter and to progressively decrease or diminish the quantity ofbinding material in the wheel from the periphery inwardly radially sothat for a fixed angular velocity, the amount of binder will be properfor any diameter to which the wheel may be worn away and reduced. 4

A further object of my invention is to provide an abrasive-wheel,preferably the high speed type, the cuttin or abrasive properties ofwhich are substantially constant when the wheel is rotated at a fixedangular velocity, irrespective of the diameter to which the wheel may bereduced.

A further object of my invention is to provide a high speed abrasivewheel, the heat of which will not be substantially increased as thediameter is reduced, due to the wearing away of the wheel in actual use.

A further object of my invention is to provide a vitrified high speedabrasive wheel which will be strong enough to withstand the impacts towhich the particles of abrasive, at the periphery thereof, aresubjected, and in which the amount of bonding material is greatest atthe periphery of the nished wheel and is progressively less and lessradially inwardly, but sufiicient to firmly bind the particles at theperiphery of the wheel irrespective of the extent to which the diametermay have been reduced in using the wheel.

A further object of my invention is to increase the quantity ofvitrifiable material in a mix for a vitrescible wheel, progressivelyoutwardlyand substantially radially, so that the I guantity of vitrifiedbonding material in the nished wheel is suflicient but not substantiallyin excess of that required to impart the necessary strength to anabrasive wheel of whatever diameter the finished wheel may be reduced inuse.

Further objects of my invention will appear in the specification andclaims below.

In the drawings forming. a part of this specification and in which thesame reference characters are employed throughout the various views todesignate the same parts,

Figs. 1 and 2 are representations, on a greatly exaggerated scale, of across-section through a few contiguous pieces of abrasive materialpacked together as they are in an abrasive wheel and with the bondingmaterial substantially coating the pieces and lining the intersticesbetween adjacent pieces of abrasive. In Fig. 1 is shown such a fragmentof an abrasive wheel with a relatively light coating of binding materialon the particles of abrasive and in Fig. 2 are shown the same piecesprovided with a thicker coating.

. These figures are to illustrate the manner in which an increasedquantity of bonding material augments or increases the bond between thecontiguous pieces of abrasive. These figures are for illustrativepurposes only and are to a great extent diagrammatic.

Fig. 3 is a fragmentary diagrammatic view of a circular mold withinwhich is plastic material out of which abrasive wheels may be made, themold and plastic material being shown in section and as mounted on theupper end of a vertical shaft adapted for rotation. This illustrates onemanner of making my improved abrasive wheel.

ig. 4 is a diagrammatic sectional View through a finished abrasive wheelafter the plastic material has been dried in the apparatus shown in Fig.3; has had an axial hole cut therein; and has been fired, vulcanized,pressed or otherwise made rigid.

Figs. 5 and 6 are diagrammatic sectional views showing a modified manneror method of making an abrasive wheel embodying my invention and adifferent mode of incorporating a progressively increasing bond from thecenter of the wheel outwardly to the periphery.

Figs. 7 to 11 are diagrammatic views illustrative of a further modifiedmethod of making an abrasive wheel and in which concentric annuli ofplastic material for making abrasive wheels are formed, each ringcontaining a little stronger or firmer bond between the abrasiveparticles than the next adjacent ring enclosed by it whereby aprogressively increasing strength of bond is secured radially outwardlyfrom the axis of the finished wheel.

Figs. 1 and 2 represent a small section of an abrasive wheel on agreatly enlarged scale,

with a few abutting or contiguous graded pieces a of carborundum orother abrasive material, packed together as in a finished abrasivewheel.

Referring to the four pieces of abrasive a a a a each piece is providedwith a coating 6 of bonding material, such as vitrified clay, fusedporcelain, bakelite, waterglass, rosin, or an other suitable binder.Between a and a of Fig. 1, the length a: of the bond is clearlyindicated, as is also the bonds w between the pieces a and a a and a;and between a and (L The same pieces a a a and a are shown in Fig. 2,with a thicker coating 5 and the extent of the bond is increased from asto an.

These two figures illustrate very strikingly how a slight increase inthe quantity of binding material substantially increases the strength ofthe bond between two contiguous particles of abrasive.

Thus by making a proper and varying distribution of the bonding materialthroughout the extent of an abrasive wheel by increasing the amount ofbonding material between contiguous pieces progressively outwardlyradially from the center of the Wheel, the part1- cles of abrasive atthe periphery of the abra sive wheel may be bonded together more firmlyand more rigidly to withstand the strains of centrifugal force and theimpact of the grains or particles of abrasive against a piece of metalwhen the wheel is rotated at the speed at which it is designed, and thepart1- cles of abrasive between those at the periphery and the insidediameter are bound together by a bonding material, the amount andstrength of which is slowly pro ressively decreased inwardly radially.Such is the abrasive wheel which constitutes my invention.

One way of forming an abrasive wheel embodying my invention isillustrated diagrammatically in Fig. 3 wherein a circular mold 1 isadapted to be firmly seated on a turntable 2 mounted on the upper end ofa spindle 3 in journals or bearings 4:, 4, in a suitable standard orframe 5, a part of which only is illustrated, it being understood thatthe frame or standard 5 may be mounted rigidly, so that the pulley 6 onthe shaft or spindle 3 may be driven from a suitable motor to efiect therotation of the turntable 2 and mold 1 mounted thereon. The mold l isfilled with a suitable plastic material C, such as carborundum, mixedwith an aqueous or colloidal dispersion of clay or other suitablevitrescible material.

After the mold has been filled to a sufiicient pulverized clay inaqueous suspension or dispersion, to flow through the water in whichthey are suspended and through the interstices between the adjacentparticles a of carborundum outwardly radlally toward the outer wall ofthe mold 1. The amount of clay or other powdered material which may thusbe thrown outwardly through the supporting liquid toward the outercircular edge of the plastic mass will depend upon the speed and lengthof time that the mold is so revolved.

As a result of this treatment, the quantity of binding material, such asvitrescible clay, in suspension in the water throughout the plastic massC, will increase gradually and progressively from the center of the moldoutwardly to the periphery. Thereafter the mold 1 is removed from theturntable and is placed in a drying room where the water is evaporatedtherefrom, leaving a greatest amount of vitrescible material at theperiphery of the dried wheel and a progressively less amount towards thecenter.

After it has been dried, the abrasive Wheel will be substantially a massof abrasive, lightly bound together by said vitrescible bindingmaterial, but the wheel will be relatively soft, somewhat of theconsistency of dried mud. By merely rotating it, a suitable central hole8 may be cut therethrough. Thereafter the mud wheel so formed is placedin a suitable kiln and fired, whereupon the vitrified clay or otherbonding material will constitute the bond between the adjacent pieces aof abrasive material in the finished wheel 9 and the bond between thepieces of abrasive material will be greater at the periphery of thewheel than at any other part of the wheel, and from the peripheryinwardly radially, gradually decreasing. 1

In Figs. 5 and 6 is shown another method of making an abrasive wheelembodying my invention. In this case the plastic material C is placed inthe circular mold 1 thicker or deeper at the periphery of the mold thanat the center. Upon the invertedconical surface of the plastic mass ofabrasive and binder material C are placed a circular series of boards orplates 10 each in the form of a sector of a circle of a diameter of theinside of the mold 1, the sectors, when they lie in a horizontal planeforming a disk of the size of the interior of the mold.

Substantially vertical pressure is then applied to the upper surface ofthe sector pieces 10 to compress more of the material into the peripheryof the plastic mix C than at the center. This maybe applied bysubjecting the segments over the mass C in the mold 1 to the action of aplunger 11. Thereafter the mold with the plastic mass in it istransferred to the drying chamber and the mass dried as previouslydescribed after which it may be hardened by vitrifyin the binder orotherwise solidifying it, i the binder be other than a vitres'ciblebinder. In this manner more bonding material is progressivelyincorporated into the wheel from the center outwardly radially and awheel 9 embodying my invention may thus be formed.

In Figs. 7 to 11 is indicated, in a somewhat diagrammatic manner, athird method of makmg an abrasive wheel 9 embodying my invention, thescale being larger in Figs. 8

hereafter referred to, is preferably a little greater than the depth ofthe mold 1, as ind cated 1n Fig. 8. Then the space between the ring 12and the inner wall of the mold 1 is filled with a plastic mixture C ofabrasive and blnder or bond in which the proportion of binder or bond tothe abrasive is what is suitable to use in a wheel of that diameter andadapted to be rotated at a predetermined glven speed. Since theproportion of the bonding material to the amount of abrasivematerial'will vary with almost every wheel that is made, depending uponthe diameter of the wheel and the speed at which it-is to be rotated, Ido notintend to limit myself to any definite proportions, because thoseproportions are well known to the mechanic skilled in the art of makingwheels of this character. The composition of the outer ring or materialwill be well understood by those skilled in the art, when it is statedthat the proportion of the bonding material to the abrasive is thatwhich has been found by pract1ce necessary in the making of wheels ofthat diameter designed to be rotated at the given high speed ofrotation.

The plastic material C having thus been placed in the outer section ofthe mold, a second ring 14 of smaller diameter is placed within it andgages 15 provided with two notches 15 on its under edge are placedthereon, the upper edges of the rings 12 and 14 fitting in the notches15 respectively of the gage 15. Then within this second annular channelso formed in the mold between the ring 12 and the ring 14 is deposited aplastic mixture C containing a little less of the bonding material or abonding material not quite so strong as that in mass 0 and this channelis thus filled with lastic material C as illustrated in Fig. 9. T en athird ring 16 still smaller in diameter is similarly placed within themold 1 and a set of gages 15 with similar notches 15 fitted over the topedges thereof. These gage strips 15 are preferably used in sets of threefor each pair of rings, spaced at 60. from each other for the pair ofrings to hold the rings in a fixed concentric arrangement While the moldis being filled. Then plastic material C having a little less bondingmaterial than the plastic material C is placed in the channel betweenthe rings 14: and 16 until this channel is filled with this plasticmaterial G. Then a still smaller ring 17 may be placed within the ring16 and held in place by a set of gage strips 15, as shown in Fig. 11 andthe space therebetween filled with a plastic abrasive material mix Cwhich contains a little less of a bonding material than that at presentin the mix C. When the space between the rings 16 and 17 is filled, thenthe gages 18 and 15 are removed and the ring 12 lifted out from betweenthe two mixes C and C This process may be repeated with smaller andsmaller rings 18 and 19 and the spacebetween each pair of adjacent ringswill be filled with a material having a less amount of bonding materialtherein than that immediately surrounding it. In this manner an exactdistribution of the bonding material or the strength of the bondingmaterial throughout the wheel radially, stronger at the periphery andgradually less strong progressively inwardly may be attained. After themold has thus been filled and the rings removed, it is dried in theusual manner and then fired or otherwise made into a solid form.

While an abrasive wheel embodying my invention might be made using plaincylindrical rings instead of the corrugated rings 12, 14, 17, etc., Iprefer the corrugated type of ring, because when the ring is removedfrom between the two adjacent annuli of slightly different mixtures theprojections on the surfaces of one annulus of plastic material projectinto corresponding recesses in the adjacent annuli of plastic materialand there is a more intimate union of the two annuli due to coinminglingand flowing of the fluid content of one ring into that of the other, andso that there will be no sharp clean cylindrical line of cleavage orsudden change in material in the finished wheel and so that there willbe a stronger and better bond between adjacent annular sections of thefinished wheel.

While this invention is particularly applicable to the making ofabrasive wheels wherein the bonding material is vitrescible, it is to beunderstood that the processes are applicable to the construction ofwheels in which other binders are used. A bakelite binder or a rubberbinder are usually colloidal in nature when mixed with the abrasive inmaking the mud cake or plastic mass and such binding readily lendsitself to the centrifugal processdescribed in connection with Figs. 3and 4, as well as to the process of packing more mixture into the moldand compressing it as indicated in Figs. 5 and 6.

The nature of the plastic mixture or mass employed in making abrasivewheels is such that it readily lends itself to any of the modes ofprocedure heretofore described. The particles of carborundum or otherabrasive are hard and rough, no matter how small the particles may beand when compacted together with portions of their surfaces inengagement and with the coating or bonding material squeezed out frombetween them in the plastic mass in the mold, those particles do notslide over each other when the plastic wheel is sub jected to a rotarymovement, but they remain immovable with small voids or unfilled spacesbetween non-contacting parts of adjacent particles of abrasive throughwhich a fluid binding material, particularly when of a colloidal nature,freely flow and in which the matter suspended in the supporting liquidare readily thrown outwardly by centrifugal force, through thesuspending medium and through the pores or passages between theparticles of abrasive toward the outer wall 01 the mold.

A wheel having a non-fluid bonding material may also readily be made bythe practice of the process illustrated in Figs, 5 and 6, for from thevery nature of the mixture it is easy to provide the plastic mass in themold with an increasing quantity of the abrasive and bonding materialand to compress the mass more at the periphery than at the center andprogressively less between the periphery and the center as described inconnection with Figs. 5 and 6.

And various bonding materials, other than those of a vitrescible naturemay be used in connection with the process illustrated in Figs. 7 to 11,for it is easy to mix a graduated series of batches of the abrasivematerial and binder and to fill the sections of an annular sectionalmold with the different grades of the mixture.

The process above described in connection with Figs. 7 to 11 may beslightly modified by varying the quality of the bonding material as thequantity of bonding material is diminished in the successive annuli ofplastic mixtures of abrasive material and bond. A stronger bondingmaterial less in quantity may be used, so that while there may be adiminution in quantity of binding material, the strength of the lesserquantity of binding material may be made equal to substantially that ofthe ring next adjacent and outside of it. In other words, I do not wishto be limited to a wheel in which the bonding material is of the. samequality throughout the wheel and the-quantity of it varied, for myinvention contemplates the use of progressively smaller quantities ofbinding material inwardly radially of the Wheel without acorrespondingly diminution in the strength of the bond.

From the above it will be seen that I have provided a new and highlydesirable'type of abrasive wheel which can in use he reduced or wornaway to a very much smaller diameter than that of the original wheel,without impairing the abrasive properties or substantially weakening thewheel when reduced in diameter and which is not subject to the heatingwhen worn due to an excess of bond between the abrasive particles, and Ihave described several methods of making such a wheel, but my inventionis not to be construed as limited to any or all of the processes hereindescribed, provided such a wheel having the physical characteristics ofmy wheel be made by the process described or other process which may belater devised.

Having thus described my invention, what I claim and desire to protectby Letters Patent of the United States is:

1. A high speed abrasive wheel composed of particles of abrasivematerial unitarily and rigidly united together by a bonding material,the proportion of bonding material to the abrasive being progressivelygreater radially outwardly from the inner diameter of the wheel to theperiphery thereof.-

2. A high speed abrasive wheel composed of particles of abrasivematerial unitarily and rigidly united together by a vitrified bondingmaterial, the proportion of bonding material to the abrasive beingprogressively greater radially from the inner diameter of said wheel tothe periphery thereof.

3. An abrasive wheel composed of particles of abrasive material rigidlyunited together by a bonding material, the proportion of bondingmaterial to the abrasive being variable and progressively greater fromthe inner diameter to the outer diameter thereof, and sufiicient at theperiphery to safely bind the particles for the highest. angular speedfor which the wheel is designed to be rotated.

4. An abrasive wheel composed of particles of abrasive materialunitarily and rigidly united together by a bonding material, thequantity of bonding material between adjacent particles of abrasive in aselected point in any diameter of the wheel being less than at any pointbetween said selected point and the periphery of the wheel and more thanat any point between said selected point, and

' the inner diameter of the wheel and sufficient to safelybind theparticles together when the active surfaces of said wheel are worn downto said selected point and is rotated at the angular speed for which theoriginal unworn wheel was designed to be rotated.

In witness whereof, I have hereunto set my hand this eighth day ofAugust,-1929.

REVERE GHAPELL,

